Testing and finishing optical elements



Dec. 20, 1927. 1,653,234

T. SMITH ET AL TESTING AND FINISHING OPTICAL ELEMENTS Filed April 4, 192,5

'INVENTORS: THOMAS SMITH JOHN HENDRI DOWELL,

/; their Attorney MM fit) . cord;

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non of different 1', to the ends of Patented Dec. 120, 1 927;

memes smrrii; or rnnnmeron, nun JOHN n nnnnr mama, or nonnoinannenann, v a v 7 Assrenons'roinnam HILGER, LIMITED, or LONDON, ENGLAND} rnsrme YAND mnrsrrmo OPTICAL ELEMENTS,

application filed April 4, iaas semai no r Amending to and finishingof optic-al elements vwhere the angle between the incident'ibeani and the.

element under test is varied for the examinai magc receiver isdisplaced towards or away fromthe element as that angle ovaries, an object i-sprovided at a finite (lISl'ZHlQB fI'ODI the ,elenient'and s caused to m image receiverso as k r e displaced conj-ointly with the displacement of the to maintain the objectin a predetermined light passes through tliereleinen't'under test and is reflected back by a spherical mirror to the partially silvered plate and re'coinbined with the other part of the light, there by indicating the faults of the element under test by the interference ringsproduced.v

Fi ures 1, 2' tandf3 cally three apparatus with this invention. the element under 2' the image receiver. upon a carriage through which passes a rod which are secured cross bars, a bar 0 b on the object side and a bar shew diagrammati- In sun-1e figures Z is i b on the image side, the object o 'and the image receiver z being kept in contact with the bars 0 b and i b respectively, for instance, by a cord passing over a pulley, there being a weight at the free end of the In Figure 2 a telescope t is in-sertedbetween the object 0 and the element Z, and the image receiver is a spherical mirror.

Figure 3 is similarto Figure 2 except that a partially silvered plate p is inserted be tween the object 0 and the telescope t, part of the light passing as before through the element Z and the other part passing to a mirror a by which it is reflected back to the plate p where it is recombined with the light passing from the element Z and thence to a lens 0 by which it is focussed to form an image at the aperture of a diaphragm 03 whereby interference rings are produced which arrange themselves into what may be called a contour map of the imperfections of the element Z. a

.'arsena -sea Britain Apr-ii 3, i924,

invention, in the testing 7 parts of the field and the "respectively both vary the eminent but linear. relationship. p Iii-the claims the words object surface and the mtended to image receiver in correct adjustment with respect to the con ugateima ge surface, The

made accordance test, ois the object and The lens I is mounted I {By this means the object is vmaintained '1 i I i .i i l r i i' V v I l i ,in a definlte object surface and the v Y image "receiver ncorrect adjustment w th respect tothel' eonjagate image surface, correspond- *ing' te' a constant magnification determined by rat-ioo'f theme arm-s01 the rod r." In otl'ier; words tl1e;di.stances from the ele entjunder testsof, theimage and object with, the rotation of always satisfy a definite optical element include lenses, prisms or mirrors, or combinationsof these, such as telescopes, and the words are intended toinclude a mirror orlens o'r image receiver system oflenses or a photographic plate or 'af ne'tal plate upon which the image-is received. V

Whatwelclaiin isg I lQIn testing and finishingofoptical elenients where theangle between the incident beam and ;.the element under testis varied forthe examinat on of different parts of the field andtheiin'age receiver is displaced towards or away frointhe element as the said angle varies, providing an object at a finite distance from the element andcausing said object to be displaced conjointly with the displacement of maintain said object in a predetermined object surface and the image receiver in correct adjustment with respect to the conjugate image surface. 1

2. In testingand finishing of optical elements where the angle between the incident beamand the element under test is varied. for the examination of different parts of the fieldand the image receiver is displaced towards or awayfrom said angle varies, providing an object at a finite distance from the element and causing said object to be displaced conjointly with the displacement of said image receiver so asto maintain said object in the object surface corresponding to a predetermined magnifieation and the image receiver in correct adjustment with respect to the conjugate image surface. a

8. In testing and finishing of optical elements where the element under test is rotated about a fixed axis for examination of different parts of the field and the image receiver is correspondingly displaced to- Wards or away from said axis, providing an said image receiver so as to the element as the i I object 'at linear relation between displacing tical elements comprising optical element to be tested, means for roa finite distance from said element and causing said object to be displaced conjointly with the displacement of said image receiver so as to maintain a predetermined the distances from said axis of the ob 'ect and image receiver respectively,

t. 'Apparatus for testing and finishing optical elements comprising a holder for the optical element to be tested, means for rotating said holder about a fixed axis, an object holder, an image receiver, and means coacting with said first mentioned means for displacing said 'ob ect holder and, said image receiver so that the distances thereof, respectively, from the said axis vary but satisfy a predetermined linear relationship.

5. Apparatus for testing and finishing op-; tical elements comprising a holderfor the optical element to be tested, means "for rotating said holder about a fixed axis, an object holder, an image receiver, a constant ratio lever said object holder and said image receiver, sail lever coacting with said means for rotating said holder for the optical element.

6. Apparatus for testing and finishing opa holder for the tating said holder about a fixed axis, an ob ject holder, an image receiver, a rodcarried by said optical element holder, and cross bars carried by! said rod'abutting against said image recelver and said object holder respectively. a

7 Apparatus for testing and finishing op tical elements compr sing a holder for the holder and said holder nient, an image receiver, a

turning about a fixed axis for.

optical element to be tested, means for rotating said holder abouta fixed axis, an object holder, a telescope between said object for the optical element, an image receiver, and means coacting with said first mentioned means for displacing said object holder and said image receiver so that the distances thereof respectively from the said axis vary but satisfy a predetermined linear relationship.

8. Apparatus for testing and finishing optical elements comprising a holder for. the optical element to be tested, means for rotating said holder about afixed axis, an object holder, a telescope between said object holder and said holder for the optical eleconstant "ratio lever turning about a fixed axis for displaceing said object holder and said imagereceiver, said. lever coacting with said means for rotating said holder for the optical element.

9. Apparatus -for testing and finishing o tical elements comprising a holder for the optical element to be tested, means for rotating said holder about a fixed axis, an object holder, a telescope between said object holder and said holder for theop'tical element, an image receiver, said optical element holder, and cross bars Carried by said rod abutting against said image receiver and said object holder respectively";

' In testimony that we claim the foregoing as our invention, we have signed our names this 27th day of March. 1925.

THOMAS SMITH. JOHN HENDRI' DOWELL.

arod carried by 

